Remove some unnecessary NULL checks.

Review Request #445 — Created Jan. 24, 2021 and submitted — Latest diff uploaded

Information

pidgin/pidgin
default

Reviewers

* When removing a buddy, the group is optional as noted in the description.
* When setting a buddy icon, the icon may be %NULL to remove existing icons.

Compile and watch for assertion failures in the log, when signing out of Bonjour, and when removing a buddy icon from an account (which did nothing.)